PHASE II REPORT - Caltrans

Table 4.5: Preliminary Evaluation of Consistency and Mixing Torque
System Consistency Mixing Torque, N-cm Mixing Time, min Spread Time, min
M1 Stiff (St) 9 – 10 3.5 4.9
M2 Moderate (MV) 8 – 9 7 >10
M3 Soupy (S)/LV 6 – 7 >10 >10
Conclusions:
The mix procedure can distinguish between very fast and fast setting systems. The procedure
can show the differences in mixing and spread time for different systems. It also shows mixing
torque correlation with the mix characteristics of TB-113.
4.2.2 Development of the Automated Cohesion Test (ACT)
The existing ISSA test method for cohesion, TB-139, uses a hand held torque wrench to apply a
load to a test specimen 0.23 inches (6mm) or 0.39 inches (10mm) in diameter depending on the
top size of the aggregate. Torque measurements are made at intervals of 30, 60, 90, 150, 210,
and 270 minutes after casting the specimens.
The major difficulty with this procedure is that the application of torque is very operator
dependent. To overcome this problem, the project team contracted with Temple Systems, Inc.
of Dayton, Ohio to develop an automated device to perform this test. The device is connected
to a computer and is controlled by software that lowers a pressure foot on the test specimen.
The operator specifies the amount of rotation of the foot at the time intervals specified. The
rotation can be set from 45 to 360 degrees. During rotation, the device transmits torque values
to the computer. When complete, the torque measurements are graphically displayed.
The “first article” design of the Automated Cohesion Test device has been developed by Temple
Systems Lab of Dayton, Ohio and it is shown in Figure 4.16. Testing on sandpaper was
completed to assure that the device functioned properly. The device was then sent to
MACTEC’s laboratory in Phoenix, Arizona, to complete the testing matrix.
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